1. Field of the Invention
The present invention relates to an apparatus for conveying and transferring workpieces such as semiconductor wafers, liquid crystal substrates, optical disks and magnetic disks or the like, a method of inspecting conveying containers, and a method of treating works and containers.
2. Description of the Related Art
Semiconductor wafers or liquid crystal substrates (hereinafter referred to as works) are accommodated in and supported by a cassette having grooves for inserting the works therein, and the cassette carrying the works is loaded into a treating apparatus or an inspection apparatus (hereinafter referred to as a treating apparatus) in a manufacturing process. The cassette carrying the works is conveyed, manually or by a trolley, from a treating apparatus to another treating apparatus. The trolley may be pushed by hand or may be electrically powered. The cassette carrying the works is set in the treating apparatus where the works are treated.
In a plant for manufacturing semiconductor devices and liquid crystal panels, the process is carried out in an atmosphere called a clean room containing an extremely small amount of foreign matter (particles) which are liable to cause defects to the products. Not only foreign matter but also gaseous molecules could contaminate the works to cause defects in the products. Further, dust from the conveying trolley and a human body becomes a cause of contamination of the works. As the works are treated very finely, the cleanliness of the clean room must be maintained very high, often making it necessary to reconstruct a clean room. Hence, costs for maintenance and management of the clean room and for reconstructing clean rooms are increasing.
In order to prevent contamination to the works caused while the works are being conveyed, there has been proposed an SMIF (standard machine interface) system. The SMIF system uses a standardized closed container called POD or FOUP (front opening unified pod) and a loading device adapted to the closed container. A cassette carrying the works is contained in a clean sealed container (POD), so that the works can be conveyed or can be placed outside the treating apparatus, without being contaminated.
The loading device is arranged by the side of the treating apparatus or is incorporated in the treating apparatus. The loading device has a support portion for placing the closed container outside the treating apparatus. The closed container containing the cassette carrying the works is conveyed to the support portion of the loading device in a desired treating apparatus by passing through an area where cleanliness is relatively low, and is placed on the support portion.
The loading device is an interface device between an area where cleanliness is relatively low and the interior in the processing apparatus in which high cleanliness is maintained. The loading device includes a container opening means for opening the closed container on the support portion, and a cassette transferring means for transferring the cassette from the container that is opened onto the treating apparatus. Therefore, the works, with the cassette, are fed into the treating apparatus, works are taken out from the cassette one by one or several ones together, by a robot, or all the works are transferred at once, and the works are treated. After the works are treated in the treating apparatus or are inspected, the works are returned back to the cassette again, and the cassette is transferred onto the support portion of the loading device. The cassette transferred onto the support portion of the loading device is contained in the closable container.
It is necessary to prepare and use standardized closed containers and loading devices adapted thereto, if the SMIF system is to be used. However, the standardized closed container is relatively expensive. It is desired to convey works using a container other than the standardized closed container. Further, a loading apparatus must be provided for each treating apparatus. Therefore, a plurality of treating apparatus require an equal number of the loading devices. Accordingly, the SMIF system becomes relatively expensive.
In addition, when works are to be conveyed using a trolley, it is desired that the trolley is provided with an air cleaning device to maintain the interior of the trolley clean. The air cleaning device usually includes a fan operated by electric power and a filter. A storage battery is mounted on the trolley to supply electric power to the fan on the trolley. However, the storage battery is so heavy that the weight of the trolley increases. Besides, a problem arises concerning handling the battery, such as an operation for electrically charging the battery. It is therefore desired to provide a trolley that is free from the above-mentioned problems yet capable of keeping the works clean. It is further desired to provide a work conveying and transferring apparatus using a trolley capable of decreasing the adhesion of particles on the works such a semiconductor wafers or liquid crystal substrates.
Further, the closed container has a base portion, a cover portion mounted on the base portion, and a locking means for locking the cover portion to the base portion. The loading device has an unlocking means for unlocking the locking means. As the closed container is used many times, the locking means of the closed container becomes damaged, the function of the locking means is deteriorated, and the members constituting the locking means are worn out and produce play.
So far, therefore, the closed container is replaced by a new one after the container is used for a predetermined period of time or is used for a predetermined number of uses. In many cases, therefore, closed containers that can be still used are often discarded, resulting in an increase in the cost. Further, the closed containers are often continuously used even after the function of its locking means has been deteriorated, causing a problem. It has therefore been demanded to inspect the closed container.
Also, when the interior of the closed container is contaminated, the container is disassembled to wash the parts. This, however, requires laborious work for disassembling and washing. It is desired to clean the closed container of the contamination without much labor. It is also desired to inspect the closed container and to clean it of the contamination in combination with the step for treating the works.
The invention is further concerned with a conveying apparatus adapted to conveying a carrier containing substrates such as semiconductor substrates.
In a process for producing semiconductor devices, the semiconductor substrates are contained in the carrier which is conveyed between, for example, two semiconductor treating apparatuses or between a stocker and the semiconductor treating apparatus. The conveying apparatus includes a conveying trolley that runs along a floor or a ceiling. The carrier containing the substrates is accommodated in a closed box which is mounted on the conveying trolley, so that the substrates will not be contaminated while being conveyed.
The closed box is lifted from, for example, the stocker and is lowered at a semiconductor treating portion. For this purpose, therefore, the conveying apparatus includes an elevator. The elevator is a hoist including, for example, a motor and a plurality of wires (or belts). The plurality of wires are attached to the closed box. Upon simultaneously winding the plurality of wires, the closed box can be elevated and lowered maintaining a horizontal attitude.
In the conventional conveying apparatus in which the carrier containing the substrates is further accommodated in the closed box, a plurality of closed boxes are required in a number equal to the number of the carriers. The closed box is expensive and is larger than the carrier. When being not used, therefore, a large space is required for storing the closed boxes.
It has therefore been desired to mount the carrier containing the substrates on the conveying trolley without using the closed box. However, since the carrier is not of a closed structure, a problem arises in that dust adheres on the substrates while being conveyed. When the carrier is conveyed by the conveying trolley, further, the substrates contained in the carrier move and vibrate, and escape from the carrier and may fall from the conveying trolley.
In elevating and lowering the substrates contained in the closed box or the carrier, there is a problem that it is difficult to elevate or lower the box or the carrier maintaining a horizontal attitude, if there is any difference in the elongation of the wires of the elevator. When the closed box or the carrier is not elevated or lowered maintaining a horizontal attitude, the box or the carrier is not lowered onto a correct position, producing a transferring miss. Therefore, the lengths of the wires must be often adjusted.